Source: http://www.abarim-publications.com/Meaning/Rephaim.html

🔼The name Rephaim in the Bible

The Rephaim are a tall and numerous people, related to the enigmatic Nephilim, Anakim, Emim (Genesis 14:5) and Zamzummim (Deuteronomy 2:20). It is said that king Og of Bashan was the last of the Rephaim (Deuteronomy 3:11). There is also mention of a Valley Of The Rephaim (Joshua 15:8, 1 Chronicles 14:9, Isaiah 17:5).

🔼Etymology of the name Rephaim

The name Rephaim is curious to say the least. It most likely has something to do with the verb רפה (rapa), sink down, let drop or be slack. Scholars insist that the name רפאים should be regarded as an other word than רפאים (repaim), meaning ghosts or shades, but we may wonder if the original audience of the Hebrew Bible was aware of that, or even cared about it. The name Nephilim, which seems to be either a synonym or else something close to one, comes from a verb that means to fall.

And while we're opposing scholarly convention, let's also point out the verb רפא (rapa'), meaning to heal. This verb is often used in the Bible to connote forgiveness and spiritual healing. See Isaiah 53:5, for instance.

🔼Rephaim meaning

It's difficult to establish how a Hebrew audience would have understood the name Rephaim. It's identical to the word denoting ghosts but it also looks like it has to do with the verb that means to heal. The Rephaim are the Faded Ones but also the Remedied, or That What We've Been Healed From. The name Zamzummim appears to mean something similar: The Dealt With.